Electronic displays are used in a wide range of applications. Some electronic displays have a spatial light modulator. Elements of the spatial light modulator are controlled in response to image data to yield an image that can be observed by viewers. The elements of some spatial light modulators are ‘binary’ elements which have two states. In one state the element passes light to a viewing area and in another state the element does not pass light to the viewing area.
A digital mirror device (DMD) is one example of a binary spatial light modulator. A DMD provides an array of mirrors. Each mirror can be switched between two states. The state of a mirror can determine whether or not light incident on the DMD at the location of the mirror will pass along a path that will take it to a viewing area. When a mirror is in an ‘ON’ state, light is directed to a location in a viewing area that corresponds to the mirror. When the mirror is in an ‘OFF’ state the light is directed along a path that does not take it to the viewing area. It is typical for light in the OFF state to be directed to a heat sink.
An element of a binary spatial light modulator can be controlled to display intermediate brightness values by rapidly turning it on and off. The brightness that will be perceived by a human observer can be altered by adjusting the relative amounts of time during which the element is in its ON and OFF states.
Some displays provide serial light modulators. In such displays, light is modulated serially by first and second light modulators. Examples of displays are described in PCT Patent Publication No. WO2003/077013 and U.S. Pat. No. 6,891,672. PCT Patent Publication No. WO2003/077013 describes a light source having an array of controllable light-emitting elements, and a spatial light modulator having an array of elements of controllable transmissivity for modulating light from the light source. U.S. Pat. No. 6,891,672 describes first and second spatial light modulators arranged in series to modulate light from a light source. Each spatial light modulator has an array of controllable pixels, wherein each pixel of one of the spatial light modulators corresponds to a plurality of pixels of the other one of the spatial light modulators.
There is a need for cost effective displays capable of providing high image quality.